C1 Titanium Cables Combined with C2 Pedicle Screw-Rod Fixation for Atlantoaxial Instability Not Suitable for Placement of C1 Screws.

Objective: We sought to develop a new posterior fusion technique composed of bilateral C1 titanium cables and C2 pedicle screw-rods for treatment of atlantoaxial instability not suitable for C1 screw placement.

Methods: A study was conducted of 18 patients with atlantoaxial instability who had C1 broken screw trajectory or anatomic anomalies. All patients underwent posterior fixation with bilateral C1 titanium cables and C2 pedicle screws. The follow-up period was a minimum 1 year. Clinical outcomes measurements included visual analog scale score for neck pain assessment, the American Spinal Injury Association Impairment Scale and Japanese Orthopaedic Association score for neurologic status and function. According to preoperative computed tomography (CT) reconstruction and CT angiography, the patients selected in this study were not suitable for C1 screw placement. Postoperative plain radiographs and CT reconstruction were performed to evaluate the reduction, bony fusion, and implant position. All outcomes were evaluated at each follow-up.

Results: The average clinical follow-up period was 24 months (range 12-36 months). All patients had complete neck pain relief at postoperative 6 months. Their neurologic symptoms had improved significantly at 1-year follow-up. Radiologic outcomes indicated good bony fusion and construction stability in all patients without implant failure at the last follow-up. No neural or vascular complications related to this technique were observed.

Conclusions: Posterior atlantoaxial fixation using C1 titanium cables and C2 pedicle screw-rod construct appears to be an effective and safe technique for treatment of atlantoaxial instability, which could be an alternative method for cases unsuitable for C1 screw placement when using C1-C2 screw fixation.